Net zero is the reduction in total greenhouse gas emitted into the atmosphere to a level equal to the total greenhouse gas removed from the atmosphere. It can apply to a business, an industry, a group of industries, a country or the world as a whole, and it can be accomplished through any combination of reducing emissions and removing them from the atmosphere. Achieving net zero is essential for limiting global warming to the 1.5 degrees centigrade above pre-industrial levels target established by the Paris Agreement.
Emission reduction can be accomplished by such means as transitioning to renewable energy sources, improving the efficiency of energy production and use, and adopting sustainable industrial, agricultural and other practices. Removal can be accomplished by reforestation and a growing variety of carbon capture technologies.
The concept of carbon neutral differs from net zero in that it typically emphasizes the offsetting of only carbon dioxide emissions and without necessarily reducing them first, whereas net zero is more comprehensive and emphasizes reductions in all types of greenhouse gas emissions, including methane and nitrous oxide, before relying on offsets for any remaining emissions.
Gross zero is a much more stringent goal than net zero in that it is the complete elimination of emissions from specific sectors without relying on offsets or removals.